Penn State researchers have identified a virus that's benign to humans but deadly to cancer.

The virus is called adeno-associated virus type 2, and the scientists showed in the lab that it kills breast cancer in three stages. That's a big deal because different stages of cancer now require different types of treatment, and it's difficult to get it just right. They published their results in Molecular Cancer.

The scientists still don't know how the virus takes down cancer, which is crucial for developing a drug or other type of therapeutic. If they figure out which viral genes are at work, some type of gene therapy might be the way to go. Or they could test drugs, or even use the virus itself as a remedy.

Other studies have shown the virus also kills cervical cancer, so it's an exciting lead. But it's a long way from petri dish to medicine. If animal studies are successful, then the treatment has to pass three rigorous phases of human trials. But since breast cancer is the most prevalent cancer in women the world and leads to the most cancer deaths in women, a potential alternative to chemo and radiation is something to cheer for.